Take a deep breath and say “Lungs.”

You might not think it, but your lungs are very complicated pieces of biological engineering. And given the job they’re tasked with (that being to deliver oxygen into the bloodstream and to release carbon dioxide into the atmosphere), it’s easy for things to go wrong. Asthma, allergies, bacteria, viral infections, and air pollution can all be blamed for a shortness of breath. And if it must be said, smoking doesn’t help either. (Click the image for a larger version, and check out the issue of Lungs from Kids Discover magazine.)